python-列表的增删查改

Posted 2020-12-29 fltkxy

转自：https://www.cnblogs.com/liuyam/p/6270062.html

列表是最常用的数据类型之一，通过列表可以对数据实现方便的存储，修改等操作。

先声明一个空列表：

>>> names = []
>>> names
[]

可以存多个值：

>>> names = ["wangwang","maomao"]
>>> names
[‘wangwang‘, ‘maomao‘]

如何取值：

>>> names[1]
‘maomao‘

如何修改：

>>> names[0] = "gougou"
>>> names
[‘gougou‘, ‘maomao‘]

增加：

>>> names.append("miaomiao")
>>> names
[‘gougou‘, ‘maomao‘, ‘miaomiao‘]

插入：

>>> names
[‘gougou‘, ‘maomao‘, ‘miaomiao‘]
>>> names.insert(2,"new")
>>> names
[‘gougou‘, ‘maomao‘, ‘new‘, ‘miaomiao‘]

删除：

第一种方法：

>>> names
[‘gougou‘, ‘maomao‘, ‘new‘, ‘miaomiao‘]
>>> del names[0]    #根据索引删除
>>> names
[‘maomao‘, ‘new‘, ‘miaomiao‘]

第二种方法：

>>> names
[‘maomao‘, ‘new‘, ‘miaomiao‘]
>>> names.remove("new")    #根据名字删除
>>> names
[‘maomao‘, ‘miaomiao‘]

查找：

>>> names
[‘maomao‘, ‘miaomiao‘, ‘wangwang‘, ‘liyang‘, ‘zhangsi‘, ‘jack‘, ‘mack‘, ‘rain‘,
‘yangle‘, ‘wangjie‘, ‘lirun‘, ‘xiaojie‘]
>>> names.index("liyang")   #查找索引
3
>>> names[3]
‘liyang‘
>>> names [names.index("liyang")] = "LiYang"  #根据索引重新赋值
>>> names
[‘maomao‘, ‘miaomiao‘, ‘wangwang‘, ‘LiYang‘, ‘zhangsi‘, ‘jack‘, ‘mack‘, ‘rain‘,
‘yangle‘, ‘wangjie‘, ‘lirun‘, ‘xiaojie‘]

统计某个姓名是否有重名：

>>> names.count("maomao")
2

排序：

>>> names
[‘maomao‘, ‘miaomiao‘, ‘wangwang‘, ‘LiYang‘, ‘zhangsi‘, ‘jack‘, ‘mack‘, ‘rain‘,
‘yangle‘, ‘wangjie‘, ‘lirun‘, ‘xiaojie‘, ‘maomao‘]
>>> names.sort()        #根据ASCII排序
>>> names 
[‘LiYang‘, ‘jack‘, ‘lirun‘, ‘mack‘, ‘maomao‘, ‘maomao‘, ‘miaomiao‘, ‘rain‘, ‘wan
gjie‘, ‘wangwang‘, ‘xiaojie‘, ‘yangle‘, ‘zhangsi‘]

从大到小排序：

>>> names.reverse()
>>> names
[‘zhangsi‘, ‘yangle‘, ‘xiaojie‘, ‘wangwang‘, ‘wangjie‘, ‘rain‘, ‘miaomiao‘, ‘mao
mao‘, ‘maomao‘, ‘mack‘, ‘lirun‘, ‘jack‘, ‘LiYang‘]

取值：

>>> names
[‘zhangsi‘, ‘yangle‘, ‘xiaojie‘, ‘wangwang‘, ‘wangjie‘, ‘rain‘, ‘miaomiao‘, ‘mao
mao‘, ‘maomao‘, ‘mack‘, ‘lirun‘, ‘jack‘, ‘LiYang‘]
>>> names[3:5]   #取第3和第4。注意：切片顾头不顾尾
[‘wangwang‘, ‘wangjie‘]
>>> names[-1]。 #取最后一个
‘LiYang‘
>>> names[-3:-1]  #倒数第三位和倒数第二位，注意永远是从左到右切片的
[‘lirun‘, ‘jack‘]

打印所有的基数位：

>>> names
[‘zhangsi‘, ‘yangle‘, ‘xiaojie‘, ‘wangwang‘, ‘wangjie‘, ‘rain‘, ‘miaomiao‘, ‘mao
mao‘, ‘maomao‘, ‘mack‘, ‘lirun‘, ‘jack‘, ‘LiYang‘]
>>> names[0::2]   #从头到尾，2为步长
[‘zhangsi‘, ‘xiaojie‘, ‘wangjie‘, ‘miaomiao‘, ‘maomao‘, ‘lirun‘, ‘LiYang‘]

array数组不能修改。

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